kernelcad

Add Path Segment

add_path_segment

Use this when you need a freeform/organic 2D outline — an eyewear brow, ergonomic grip, sneaker midsole, or body silhouette — by appending a curved segment to an existing PathBuilder chain on the named chain_anchor variable. The call is injected at the END of the chain, immediately before any .close(). One segment kind, selected by kind:

'spline' — .spline(points, opts?): interpolates through every points waypoint (Vec2[] mm, >= 2 entries; points[0] must match current pen position). Optional tension, and startTangent/endTangent 2D direction vectors that constrain the first-derivative direction at the endpoints (magnitude normalised internally). Use for organic 2D outlines (eyewear brow, ergonomic handle, sneaker midsole).
'nurbs' — .nurbsSegment(controlPoints, opts?): explicit B-spline net (Vec2[] mm, >= degree+1 entries; controlPoints[0] must match pen; pen ends at controlPoints[N-1]). Optional degree (default 3), rational weights (strictly positive), explicit knots (length = controlPoints.length + degree + 1).
'hermite' — .hermiteG2(a, b): each endpoint { point: Vec2, tangent: Vec2, curvature?: Vec2 } in mm (a.point must match pen; pen ends at b.point). curvature defaults to [0,0] (G1); pass matching curvatures for G2 blends. Tangent magnitude is the first derivative (~ chord length), NOT unit length. Returns the modified code + diagnostics from re-evaluating. Side-effect-free. Each kind fails closed on its own missing required params.

Input Schema

TableJSON Schema

Name	Required	Description
`a`	No	kind:'hermite' — start endpoint; point must match current pen position within 1e-6 mm.
`b`	No	kind:'hermite' — end endpoint; pen ends at b.point.
`code`	Yes	The .kcad.ts source code.
`kind`	Yes	Which path-segment kind to append.
`knots`	No	kind:'nurbs' — optional explicit knot vector; length must equal controlPoints.length + degree + 1.
`degree`	No	kind:'nurbs' — B-spline degree (default 3).
`points`	No	kind:'spline' — waypoints as Vec2 pairs in mm; at least 2 entries; first must match current pen position.
`tension`	No	kind:'spline' — optional Catmull-Rom-style stiffness; forwarded to the underlying B-spline approximation.
`weights`	No	kind:'nurbs' — optional rational weights (one per control point; strictly positive).
`endTangent`	No	kind:'spline' — optional [x, y] direction vector at points[N-1]. Magnitude is normalised internally; direction matters.
`binding_name`	No	Reserved for future use; the segment injection mutates the chain anchor in place.
`chain_anchor`	Yes	JS identifier of an existing PathBuilder binding (e.g. `const brow = path().moveTo(0,0)`).
`startTangent`	No	kind:'spline' — optional [x, y] direction vector at points[0]. Magnitude is normalised internally; direction matters.
`controlPoints`	No	kind:'nurbs' — control-net vertices as Vec2 pairs in mm; at least degree+1 entries.

Output Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedOct 11, 2026

removedOutput schema / properties

Removed value: -{
-  "binding_name": {
-    "description": "JS const name bound to the new construct (when one was created).",
-    "type": "string"
-  },
-  "diagnostics": {
-    "description": "Diagnostics from re-evaluating the modified source.",
-    "items": {
-      "additionalProperties": true,
-      "type": "object"
-    },
-    "type": "array"
-  },
-  "error": {
-    "description": "Failure message (present when ok is false).",
-    "type": "string"
-  },
-  "new_code": {
-    "description": "Modified .kcad.ts source (present on success). Caller persists it.",
-    "type": "string"
-  },
-  "ok": {
-    "description": "Whether the edit applied and re-evaluated cleanly.",
-    "type": "boolean"
-  }
-}

removedOutput schema / required
```
Removed value: -[
-  "ok"
-]
```

Changed7 schema fields changedJul 18, 2026
- addedInput schema / properties / a / properties / curvature / description
```
Added value: +"Optional second derivative; defaults to [0, 0] (G1-only)."
```
- addedInput schema / properties / a / properties / point / description
```
Added value: +"Endpoint position in mm."
```
- addedInput schema / properties / a / properties / tangent / description
```
Added value: +"First derivative (~ chord length), NOT unit length."
```
- changedInput schema / properties / b / description
```
Previous value: -"kind:'hermite' — end endpoint."New value: +"kind:'hermite' — end endpoint; pen ends at b.point."
```
- addedInput schema / properties / b / properties / curvature / description
```
Added value: +"Optional second derivative; defaults to [0, 0] (G1-only)."
```
- addedInput schema / properties / b / properties / point / description
```
Added value: +"Endpoint position in mm."
```
- addedInput schema / properties / b / properties / tangent / description
```
Added value: +"First derivative (~ chord length), NOT unit length."
```

Changed1 schema field changedJun 19, 2026

addedInput schema / allOf

Added value: +[
+  {
+    "if": {
+      "properties": {
+        "kind": {
+          "const": "spline"
+        }
+      }
+    },
+    "then": {
+      "required": [
+        "points"
+      ]
+    }
+  },
+  {
+    "if": {
+      "properties": {
+        "kind": {
+          "const": "nurbs"
+        }
+      }
+    },
+    "then": {
+      "required": [
+        "controlPoints"
+      ]
+    }
+  },
+  {
+    "if": {
+      "properties": {
+        "kind": {
+          "const": "hermite"
+        }
+      }
+    },
+    "then": {
+      "required": [
+        "a",
+        "b"
+      ]
+    }
+  }
+]

Changed1 schema field changedJun 19, 2026

removedInput schema / allOf

Removed value: -[
-  {
-    "if": {
-      "properties": {
-        "kind": {
-          "const": "spline"
-        }
-      }
-    },
-    "then": {
-      "required": [
-        "points"
-      ]
-    }
-  },
-  {
-    "if": {
-      "properties": {
-        "kind": {
-          "const": "nurbs"
-        }
-      }
-    },
-    "then": {
-      "required": [
-        "controlPoints"
-      ]
-    }
-  },
-  {
-    "if": {
-      "properties": {
-        "kind": {
-          "const": "hermite"
-        }
-      }
-    },
-    "then": {
-      "required": [
-        "a",
-        "b"
-      ]
-    }
-  }
-]

Changed1 schema field changedJun 15, 2026

addedInput schema / allOf

Added value: +[
+  {
+    "if": {
+      "properties": {
+        "kind": {
+          "const": "spline"
+        }
+      }
+    },
+    "then": {
+      "required": [
+        "points"
+      ]
+    }
+  },
+  {
+    "if": {
+      "properties": {
+        "kind": {
+          "const": "nurbs"
+        }
+      }
+    },
+    "then": {
+      "required": [
+        "controlPoints"
+      ]
+    }
+  },
+  {
+    "if": {
+      "properties": {
+        "kind": {
+          "const": "hermite"
+        }
+      }
+    },
+    "then": {
+      "required": [
+        "a",
+        "b"
+      ]
+    }
+  }
+]

Changed1 schema field changedJun 15, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "additionalProperties": true,
+  "properties": {
+    "binding_name": {
+      "description": "JS const name bound to the new construct (when one was created).",
+      "type": "string"
+    },
+    "diagnostics": {
+      "description": "Diagnostics from re-evaluating the modified source.",
+      "items": {
+        "additionalProperties": true,
+        "type": "object"
+      },
+      "type": "array"
+    },
+    "error": {
+      "description": "Failure message (present when ok is false).",
+      "type": "string"
+    },
+    "new_code": {
+      "description": "Modified .kcad.ts source (present on success). Caller persists it.",
+      "type": "string"
+    },
+    "ok": {
+      "description": "Whether the edit applied and re-evaluated cleanly.",
+      "type": "boolean"
+    }
+  },
+  "required": [
+    "ok"
+  ],
+  "type": "object"
+}

AddedJun 13, 2026

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